Context: this report comes from a RenderFuzz-based UE 5.5 rendering anomaly study. I am posting the issue publicly so other Unreal Engine developers can check whether it is reproducible, already known, or has a practical workaround.
I am seeing reflected emissive objects become temporally unstable in UE 5.5. The reflected emissive contribution appears to leave stale/double images or flicker.
Repro setup:
- UE 5.5 on Windows.
- A bright emissive sphere/object visible directly and in a mirror or glossy reflection.
- TAA or TSR enabled.
- Lumen GI/reflection path or the exact settings from conditions.json.
- Slow camera movement while the emissive object remains visible in the reflection.
Observed result:
The reflected emissive image flickers. In some captures, the reflection keeps a stale contribution from a previous frame, producing a ghosted/double image. In a related case, the reflected emissive object develops a ring/halo artifact.
Expected result:
The reflected emissive contribution should update consistently with the camera path and should not leave stale temporal data in the reflection.
I also submitted this through the Unreal Engine Bug Submission Form and am using this thread to keep a public reproduction record.
Attachment note: I attempted to attach video_comparison.mp4 here, but this forum account is currently blocked by the forum’s new-user attachment restriction. The representative video was attached to the Unreal Engine Bug Submission Form submission and can be provided again when the forum allows attachments.